Instrument Calibrations and Testing

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

detector geometry should be known when performing the primary calibration. Primary

calibration should be performed at least annually.

Standards referenced in Section 3.5.2 discuss specific performance testing of radiation

detection instruments. Testing procedures in these standards should be used for periodic

requalification of instruments or detailed testing of instruments.

The calibration of photon monitoring instruments over the energy range from a few keV to

300 keV is best accomplished with an x-ray machine and appropriate filters that provide

known x-ray spectra from a few kiloelectron volts to approximately 300 keV. Radionuclide

sources should be used for higher energies. Most ion chambers used to measure photon

radiations have a relatively flat energy response above 80 to 100 keV; 137Cs or 60Co are

typically used to calibrate these instruments. These sources also may be used to calibrate

Geiger-Mueller (GM) type detectors used for dose rate measurements. It should be noted

that some GM detectors (e.g., those with no energy compensation) can show a large energy

dependence, especially below approximately 200 keV. GM detectors should not be used if

not energy compensated.

The calibration of alpha-detection instruments normally should be performed with 239Pu,

241

Am, or 230Th sources. Several sources of different activities should be used to calibrate

different ranges.

Whenever possible, beta detectors should be calibrated to the beta energies of interest in the

workplace. A natural or depleted uranium slab source can be used for calibration of beta

detectors when beta radiations in the workplace have energies similar to the uranium.

International Organization for Standardization beta sources should be used for all other

purposes: the energy dependence of beta detectors can be tested using the calibration

sources listed in the ISO Publication 1980 (1984); these include 90Sr, 90Y, 204Tl, and 147Pm.

The calibration and testing of crucial monitoring systems are extremely important to the

overall radiation protection program but have often been neglected. Effluent monitoring and

sampling systems and remote area monitoring systems (RAMs) should be given several

tests. The radiological, environmental, and mechanical characteristics of the instrumentation

portion of the system should be fully evaluated prior to its first use to ensure its

compatibility with performance requirements and facility operating conditions. The effluent

sampling losses from the sample probe to the collector/detector should be determined. This

test should be repeated at least annually and when a significant change in the sampling

equipment is made. The sample probe should be examined at least once a year to verify that

its design or performance has not been changed by corrosion. The recorder of the sample

flow rate should be calibrated when it is installed and annually thereafter. The operability of

the overall system should be completely tested once, with repeat tests only after

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